Fluid pulsing means for print hammers



DBC- 1, 1954 w. G. WADEY 3,159,099

PULSING MEANS FoR PRINT HAMMERS led Aug. 16, 1961 FIG. l

coNTRoL PREssuREs 56 souRcEs ATTORNEY` Dec- 1, 1964 w. G. WADEY 3,159,099

FLUID PULSING MEANS FOR PRINT HAMMERS Filed Aug. 16,I 1961 2 Sheets-Sheet 2 A TTORNE YS 4 United States Patent O 3,159,099 FLUIB PULSNG MEANS FR PRINT HAMMERS Walter Georey Wadey, Wynnewood, Pa., assigner to Sperry Rand Corporation, New York, NX., a corporation of Delaware Fieti Aug. 15, 1961, Ser. No. 131,911 2 Claims. (Cl. lol- 1) The present invention relates to apparatus for,converting energy of relatively long duration into impulse energy of relatively short duration, and more particularly, to a fluid variable linkage mechanism for actuating the print hammer in a print in a mechanism.

There are several types of variable mechanical linkage in existence which, by uncoupling, convert the energy of a moving mass to an impact force. One familiar example is the typical piano or typewriter linkage whereby, after pressing the key for a certain distance, momentum is thereby imparted to the linkage which is eventually transferred to the hammer. 'Howeven in such a complex mechanical linkage, the wear and tear upon the moving contact surfaces therein causes the relatively early deterioration of the component parts. The present invention obviates the above diiculties by providing means of imparting ever increasing momentum to a mass over a relatively long period of time, after which the mechanical advantage of the system changes to uncouple the mass in motion from its source of momentum and allow it to transfer its energy by an impulse force. Only two moving parts at most need be included in the present invention, which thereby renders its construction inexpensive compared to complex mechanical linkage. Furthermore, the means of imparting momentum to the moving mass may be by a relatively low pressure iiuid pulse applied thereto. Thus, the invention is particularly adapted for use in the newly developing iield of pneumatic data processing systems where it finds direct application in printing mechanisms and the like.

It is therefore an object of the prsent invention to provide apparatus for converting low pressure pulse energy of relatively long duration into impulse energy of relatively short duration.

Another object of the present invention is to provide apparatus whereby the momentum or a moving mass may be imparted to another movable mass as an impulse force without the need of a mechanical linkage therebetween.

Another object of the present invention is to provide apparatus whereby the energy in a low pressure pulse of relatively long duration may be converted into a high pressure pulse of relatively short duration.

A further object of the present invention is to provide a printing mechanism having a print hammer actuated by momentum exchange in which only one moving part is` required.

Another object of the present invention is to provide printing mechanism whereby a low pressure i'luid pulse of relatively long duration may be used to rapidly impart momentum to a print hammer therein.

These and other objectsof'the present invention will become apparent during the course of the following description, which is to be taken in conjunction with the drawings, in which:

FIGURE l discloses the invention in a printing mechanism environment. t

FIGURE 2a discloses a pictorial cross-sectional View of the present invention.

FIGURE 2b discloses a cross-sectional elevation view of the present invention.

FIGURE 3 is a graph showing volume and pressure relationships in the present invention; and

ICC

FIGURE 4 discloses the sequence of operations occurring in the present invention.

FIGURE 1 shows the invention being employed in a printing mechanism for actuating the print hammer, wherein pulses of fluid energy are utilized to impart momentum to only one moving part other than said hammer. The numeral 10 generally indicates a housing having a number of passageways 141 through 14N in which are slidably disposed respective plungers 121 through 12N. Connected to one end of each plunger and exterior to housing 1G is a print hammer 161 through 16N. Each plunger 12 is normally retracted into housing 10 within its associated passageway 14 unless it is desired to print a character in the associated column on a print receiving member 18. Adjacent each print column on print receiving member 18, and on the opposite side thereof from print hammer 16, is a type font 24 which contains a plurality of type characters therein. The type font for each print column may be placed around the periphery of a rotating print drum 2e journaled on spindle 22 such as is shown in FEGURE l. Alternatively, each type font may be positioned on an individual type wheel. Upon rotation of drum 20, each type character is moved in succession adjacent to the print receiving member 18. When a type character to be printed is thereby moved into print position, a plunger 12 is forced outwardly from housing 1G at high speed such that its print hammer 16 drives print receiving member 18 against the type character to leave an impression thereon. The print hammer 16 rebounds from the impact with the type character and is repositioned within passageway 14.

T he means for actuating plunger 12 comprises the invention disclosed herein. Within housingl are disposed a plurality of chambers 261 through 26N, each having one end connected with an associated passageway 141 through 14N. Slidably disposed within a chamber 26 is a piston member 2S having end limits of travel between the two ends of the chamber. At the opposite end of chamber 26 from passageway 14 is a port 32 connected exterior to housing 19 with a conduit 34. Each conduit is connected toa control pressure source 36, whereby a uid pulse of relatively long duration may be applied therethrough tolchamber 26. Each piston member 28 may be fitted with an elastomer O-ring 30 or some other suitable seal, which prevents the leakage of iiuid from port 32 into the charnber volume ahead of said piston. Thus, chamber 26 can be considered as divided into two regions 38 and 49 respectively forward and aft of seal 3Q, whose volumes vary as piston 28 moves.

FIGURES 2a and 2b respectively show pictorial and side elevation views in section of the invention. As shown, chamber 26 is elongated and in the preferred embodiment has a circular cross section. Piston 2S fits snugly within chamber 26 and may be provided with the O-seal 3i) in order to isolate the two volumes 38 and 4t) one from another. The front of piston 28 may be streamlined by'shaping it in the form of an ogive 29. It the piston is so streamlined, then the lfront end 27 of chamber 26 should be complementarily shaped such that the piston front end and the chamber front end will t snugly together to a substantial degree. Passageway 14 opens into the front end 27 of chamber 26 such that the pressure existing in volume 3S can be applied against one end of plunger 12 slidably disposed therein.

Referring now to FIGURE 2b and FIGURE 3, the general principle behind the operation of the invention will be described. As can be seen from FIGURE 2b, the volume of chamber 26 is divided into two regions 38 and 40 which are respectively in front of and behind piston 2%. These two volumes are sealed from each other by means of the O-ring 30 or the like. When piston 28 is located in its extreme leftmost position, i.e.,

adjacent to port 32, volume 38 is relatively large compared with volume 46. When piston 28 moves to the right, then volume E58 becomes progressively smaller while volume l increases in magnitude. Volume 38 decreases in linear fashion as piston 28 travels toward end 27 of chamber 26 which is illustrated in FIGURE 3 by dotted line A under the assumption that the shapes of the piston front end 29 and chamber end 27 are such that volume 38 is substantially equal to Zero when piston 28 is in its extreme right hand position.

According to Boyles law, the volume occupied by an ideal compressible fluid varies inversely as its absolute pressure assuming that its temperature remains constant, Boyles law may be expressed as follows:

where P1 is the pressure of the gas of volume V1 while P2 is the pressure of the gas of volume V2. This law is illustrated in FIGURE 3 whereby it is seen that at the piston position indicated by I, the magnitude of volume 38 (line-A) is maximum while the volume 38 pressure (line C) is minimum. At piston position II, volume 38 is one-half its value at position I, while volume 38 pressure is twice its value at position I. At position III, volume 38 is one-fourth its value at position I, while the pressure is four times its initial value. At position IV, volume 38 is one-eighth its value at position I while the pressure is eight times its initial value. At position V this volume and its pressure are again respectively onehalf and double their values at position IV.

Assuming in FIGURE 2b that volume 38 has a value substantially equal to zero when piston 28 is in its extreme right hand position, i.e., adjacent end 27 of chamber 26, it will be seen from FIGURE 3 that the piston travels three-fourths of its total travel, beginning at point I with the volume 38 pressure only being increased by a multiple of four. At this time, piston 28 is in a position indicated by III. Upon piston 28 moving from position III to position IV, which yis but one-eighth the total distance between its limits of travel, the volume 38 pressure becomes eight times its value at position I. Upon piston 28 reaching point V from point IV, which is one-sixteenth the total travel, the volume 38 pressure becomes sixteen times its value at position I. Therefore, the rate of change in the pressure of volume 38 increases as piston 28 moves to reduce said volume, although the rate of change of volume 38 remains constant with respect to piston position.

When piston 28 is in its left most position, i.e., adjacent the end containing port 32, an unbalanced force must be applied thereto in order to initiate its movement toward end 27 of chamber 26. This unbalanced force is created in the present embodiment by introducing a uid pressure pulse via port 32 into volume 40 of chamber 26. If the pressure of this iuid pulse as applied against the rear end of piston 28 is higher than the pressure existing in volume 38 at this time, then an unbalanced force is created having a direction toward end 27. Piston 28 thus begins to accelerate toward end 27 and continues to do so as long as anV unbalanced force is maintained upon it in this direction. As piston 28 accelerates; its velocity and consequently its momentum increases. However, as Volume 38 is reduced its pressure increases which thus diminishes the value of the unbalanced force acting on piston 28 and consequently reduces its acceleration. When the pressure of volume 38 is finally equal to the pressure in volume 40, neglecting any effects of friction, there is no unbalanced force acting on piston 28 and thus no change in its velocity or momentum. However, because it now possesses momentum, piston 28 continues to move towards its right-most position thus reducing volume 38 even further and consequently increasing the pressure therein. Since this pressure now rises above the pressure in volume 40, an unbalanced force is applied to piston 28 in a direction opposing its motion, which thereby produces a deacceleration effect. At this time, thevelocity and momentum of piston 28 begins to decrease until eventually the piston is stopped.

The above described action is illustrated in FIGURE 3. As before mentioned, when piston 28 is at its extreme left most position, i.e., at position I, the pressure existing in volume 38 is that represented by curve C. This pressure may be made as small as desired. The pressure of the uid applied to volume 40 is represented by line B which is considered to apply a force to piston 28 in a direction opposite to the force applied by pressure C. It the input pressure B is higher than pressure C existing in volume 38 at position I, the resultant unbalanced pressure acting on piston 28 has a value indicated by curve D in FIGURE 3. This unbalanced pressure D creates an unbalanced force which causes piston 28 to move from its left most position I towards its right most position.

As piston 28 moves in the direction indicated, the pressure in volume 38 begins to increase as indicated by curve C. However, since the initial pressure C is small compared with the input pressure B, the piston moves to position II without substantially aliecting the resultant pressure D. Therefore, although piston 28 moves from Y position Ito position II and thus decreases the Volume 3S by half, the unbalanced force acting on piston 28 during this time does not substantially decrease. This means that the piston undergoes almost constant acceleration during this time. As piston 28 moves from piston II to positions III, IV, etc., pressure C grows larger at an ever increasing rate. Therefore, the acceleration of piston 28 becomes smaller, although its velocity still increases. Eventually, pressure C becomes as large as input pressure B such that the resultant pressure D drops to Zero. At this point, piston 28 no longer accelerates but instead maintains the velocity and momentum imparted to it by this time. However, because of this momentum the piston continues to move toward its right most position which consequently reduces volume 38 even more `and further increases pressure C. The resultant pressure thereby becomes negative and acts as an ever increasing unbalanced force on piston 28 in a direction to oppose its motion. Piston 28 isthereby brought to a rapid halt near or at the end of its right most travel at the time when volume 38 becomes quite small and its pressure quite large.

The eltect of the pressure C upon plunger 12 will now be described. In order to impart velocity and consequently momentum to plunger 12 in a direction away from chamber 26, there must be an unbalanced force acting thereon. Normally, plunger 12 may be maintained in its retracted position by'using either the external environmental pressure or by physical restraining means such as spring tension, etc. When the force exerted by the pressure C upon plunger 12 is less than this restraining force, plunger 12 will remain in its retracted position. However, upon pressure C becoming large enough, the resulting unbalanced force on plunger 12 causes it to accelerate in a direction away from end 27 of chamber 26. This acceleration depends upon the magnitude of the unbalanced force and thus upon the magnitude of pressure C in reduced volume 38.

In again examining FIGURE 3, it is noted that if the external restraining pressure upon plunger 12 is equal to the value shown as indicated by line E, pressure C will not exceed same until piston 28 is near the end of its travel in this direction. At this time, pressure C changes at an ever increasing rate such that the unbalanced force iacting on plunger 12, as indicated by curve F, rapidly increases to a large value in a very short time. Thus, although plunger 12 does not begin to move until piston 28 reaches a point near its end of travel, it is seen that its initial large acceleration will impart large velocity and momentum to plunger 12 Vwithin a very short space of time. A large force acting upon a mass in a short period of time is defined as an impulse (FT) and the following equation defines the change of momentum given to a mass by said impulse.

where F is the unbalanced force, T is the time said `force is applied, MVf is `the final momentum, and MVo is the initial momentum.

It can, therefore, be appreciated from the above that the energy contained in a relatively low pressure fluid pulse of long duration is imparted to a mass in the form of a relatively high energy pulse of short duration without need for any mechanical linkage. This invention is therefore particularly adapted for use with data processing equipment where information is transmitted by means of fluid pulses. It is further to be noted that the pressure of the input fluid pulse during its duration can remain relatively constant or may instead commence to decrease due to the expanding volume 40 if a constant pressure source 36 is not available. Although a decreasing input pressure would result in a more rapid change of the resultant pressure D, this does not affect the operation of the invention as long as the pressure in reduced volume 38 can build up to a point sufficient to impart relatively high velocity to plunger 12 within a short period of time. Depending upon the'particular environment in which the invention is utilized, the absolute values of the input pressure, the initial low pressure in volume 38, and the final pressure of volume 38 may be varied according to the teachings and relationships here disclosed. Furthermore, although a fluid pulse is here utilized to impart momentum to piston 28, itis obvious that other means may be employed for this purpose without changing the relationships between piston 28, volume `38, and plunger 12.

It has before been noted that print hammer 16 forces the print receiving member 18 into a type character face. This impact is sufficient to create a permanent impression in lthe print receiving material. Plunger 12 normally rebounds from the impact and is repositioned in passageway 14. In a particular embodiment of this invention, although not limited thereto, plunger 12 may be caused to have sufficient rebound energy so as to cause the production of a back pressure Wave. This back pressure helps to reposition piston 28 in its left most position in readiness for the next fluid pulse. The creation of this plunger rebound energy is itself a direct function of the initiating pulse pressure, since the momentum originally imparted to piston 28 is a direct consequence of said initiating pulse pressure. The advantages of such an ernbodirnent is that a faster cycle time results from this forceful repositioning of the piston and plunger.

As shown in FIGURE 2b, the front end of piston 28 can be streamlined if desired by giving it the shape of a ogive. Such streamlining reduces friction loss in the uid such that piston 28 gains momentum much more quickly. Other streamlined shapes may be employed to perform this function.

FIGURE 4 is a graphical timewise representation of the operation of the invention in FIGURE 2b and shows one complete cycle from the initiation of a fluid input pulse to the repositioning of piston 28 in its left most position.l Parts a, b, c, and d of FIGURE 4 respectively show the input pressure pulse, the chamber 38 volume, piston 28 momentum, and plunger 12 momentum as plotted against the cycle time. Piston momentum and plunger momentum are shown as having both positive and negative values to indicate the direction of motion.

If piston 28 is initially positioned adjacent to port 32, a uid input pulse applied thereto creates an unbalanced force in a direction toward plunger 12. Assume for purposes of this description that the input pulse pressure remains constant with the ever increasing volume 4t) until the pulse is terminated. If the initial pressure in volume 38 is quite low as compared with the input pressure, this unbalanced force is substantially constant until volume 38 is reduced by at least one-half. Therefore, the initial acceleration of piston 28 is substantially constant until position II is reached, and its velocity increases in linear fashion. This is illustrated in FIGURE 4c wherein the piston momentum is seen to also increase in linear fashion during the rst part of the cycle. However, this constant rate of change in piston velocity results in an ever increasing rate of change in volume 38. Thus, in FIG- URE 4b, it is seen that volume 38 decreases at ever increasing rate. Eventually, volume 38 decreases to such an extent that the pressure therein begins to substantially oppose the input pressure until at last there is no unbalanced force acting on piston 28 so that its velocity at this instant is unchanging. This is indicated in FIGURE 4c by the maximum positive value of the piston momentum. Thereafter this momentum curve rapidly falls to zero with a relatively high pressure being created in the reduced volume 38 sufficient to create an unbalanced force on plunger 12 and impart momentum thereto as indicated by FIGURE'4d. The high unbalanced force on plunger 12 results in a rapid increase of its momentum from a value of zero. Y

The input pulse in FIGURE 4a may be terminated either prior to, at, or subsequent to the time when momentum is imparted to plunger 12. Thereafter, the high pressure in reduced volume 38 causes an unbalanced force to be applied to piston 28 in a direction such that piston 28 quickly stops and reverses its direction of travel. This action is illustrated in FIGURE 4c by the negative portion of the curve. Because of the high pressure in reduced volume 38, to' which is coupled the rebound energy of plunger 12, a large acceleration is imparted to piston 28. As shown in FIGURE 4d, plunger 12 upon making impact with its print receiving member rebounds in the opposite direction. This is indicated by the change of polarity of the curve, wherein it is seen that the repositioning time of plunger 12 is quite'rapid. The large acceleration given piston 28 allows it to quickly traverse the distance from end 27 to port end 32. This, of course, assumes that the input pressure pulse is terminated such that little or no pressure builds up in volume 40 as it is reduced. At the end of the cycle, piston 28 is repositioned and awaits a subsequent fiuid actuating input pulse.

While only one embodiment of the invention has been shown and described, it is apparent that many modifications may be made thereto by one skilled in the art without departing from the spirit of the invention as defined in the appended claims.

I claim:

1. Apparatus for converting fluid energy of relatively long duration into impulse energy of relatively short duration, which comprises in combination: an elongated fluid impervious chamber having a wall at at least one end thereof for preventing the escape of fluid therefrom; a piston member of predetermined mass and having first and second opposed end surfaces which is slidably disposed within said chamber with its said first end surface facing said chamber one end wall so that there is substantially no uid leakage between said chamber and said piston member, said piston member being movable between predetermined maximum and minimum distances with respect to said chamber one end wall so as to vary the chamber volume between it and said chamber one end wall between predetermined maximum and minimum volume values; a pressurized body of compressible uid occupying said chamber volume; a movable mechanical force transmitting member extending through said chamber at said one end so as to be in fluid communication with said chamber volume without permitting any substantial escape of fluid therefrom, and which is normally biased to a rest position but movable therefrom in respouse to compressible fluid pressure only when below a first chamber volume value greater than said minimum volume value but less than one-fourth of said maximum volume value; and fluid source means `for selectivelyV applying for a predetermined time period motive uid of predetermined pressure against said piston member second end surface so as to impart momentum thereto in the direction yof said chamber one end wall, Where said motive fluid pressure, said piston member mass, said predetermined distances, and said predetermined time period are such, relative to one another, that application of said motive Huid t Said piston member when et ,Said maximum distance frornsaid chamber one end wall causes said piston member to have momentum in the direction toward said chamber one end Wall sufficient to create a second chamber volume value less than said iirst chamber volume value.

2.. Printing mechanism comprising: a type face, a print hammer spaced apart from said type face a distance to permit insertion of a print receiving member therebetween; an elongated uid impervious hamber having a wali at at least one end thereof for preventing the escape of uid therefrom; a pistonvmember of predetermined mass and having first and second opposed end `surfaces which is slidably disposed Within said chamber with its said first end surface Afacing said chamber one end Wall so that there is substantially no uid leakage between said chamber and said piston member, said piston member being movable between predetermined maximum and minimum distances with respect to said chamber one end wall so as to vary the chamber volume between it and said chamber one end wall between predetermined maximum and minimum volume values; a pressurized body of compressible'fluid oecupying said chamber volume; a movable mechanical force transmitting member corineeted at one end thereof to said print hammer for moving same to force a said inserted print receiving member against said type face, and Whose other end extends through said chamber at said one end so as to be in fluid communication With saidchamber volume Without permitting any substantial escape of fluid therefrom, said mechanical force transmitting member being normally biased to a rest position but movable therefrom in response to compressible fluid pressure only when below a rst chamber volume value greater than said minimum volume value but less than one-fourth of said maximum volume value; and fluid source means for selectively applying ,for a predetermined time period motive fluid of predetermined pressure against said piston member second end surface so as to impart momentum thereto in the direction of said chamber one end wall, where said motive fluid pressure, said piston member mass, said predetermined distalles, and said predetermined time period are such, relative to one another, that application of said motive fluid to said piston member when at said maximum distance from said chamber one end Wall causes said piston member to have momentum in the direction toward said chamber one end wall sufficient to create a second chamber volume value less than said rst chamber volume Value.

References Cited in vthe iile of this patent UNITED STATES PATENTS 1,031,526 Cloud r. July 2, 1912 1,055,857 Behr Mar. 11, 1913 1,555,655 Gibson sept. 29, 1925 1,691,170 schmidt Nev. 13, 192s r2,546,114 Tripien s Mar. 2o, 1951 

1. APPARATUS FOR CONVERTING FLUID ENERGY OF RELATIVELY LONG DURATION INTO IMPULSE ENERGY OF RELATIVELY SHORT DURATION, WHICH COMPRISES IN COMBINATION: AN ELONGATED FLUID IMPERVIOUS CHAMBER HAVING A WALL AT AT LEAST ONE END THEREOF FOR PREVENTING THE ESCAPE OF FLUID THEREFROM; A PISTON MEMBER OF PREDETERMINED MASS AND HAVING FIRST AND SECOND OPPOSED END SURFACES WHICH IS SLIDABLY DISPOSED WITHIN SAID CHAMBER WITH ITS SAID FIRST END SURFACE FACING SAID CHAMBER ONE END WALL SO THAT THERE IS SUBSTANTIALLY NO FLUID LEAKAGE BETWEEN SAID CHAMBER AND SAID PISTON MEMBER, SAID PISTON MEMBER BEING MOVABLE BETWEEN PREDETERMINED MAXIMUM AND MINIMUM DISTANCES WITH RESPECT TO SAID CHAMBER ONE END WALL SO AS TO VARY THE CHAMBER VOLUME BETWEEN IT AND SAID CHAMBER ONE END WALL BETWEEN PREDETERMINED MAXIMUM AND MINIMUM VOLUME VALUES; A PRESSURIZED BODY OF COMPRESSIBLE FLUID OCCUPYING SAID CHAMBER VOLUME; A MOVABLE MECHANICAL FORCE TRANSMITTING MEMBER EXTENDING THROUGH SAID CHAMBER AT SAID ONE END SO AS TO BE IN FLUID COMMUNICATION WITH SAID CHAMBER VOLUME WITHOUT PERMITTING ANY SUBSTANTIAL ESCAPE OF FLUID THEREFROM, AND WHICH IS NORMALLY BIASED TO A REST POSITION BUT MOVABLE THEREFROM IN RESPONSE TO COMPRESSIBLE FLUID PRESSURE ONLY WHEN BELOW A FIRST CHAMBER VOLUME VALUE GREATER THAN SAID MINIMUM VOLUME VALUE BUT LESS THAN ONE-FOURTH OF SAID MAXIMUM VOLUME VALUE; AND FLUID SOURCE MEANS FOR SELECTIVELY APPLYING FOR A PREDETERMINED TIME PERIOD MOTIVE FLUID OF PREDETERMINED PRESSURE AGAINST SAID PISTON MEMBER SECOND END SURFACE SO AS TO IMPART MOMENTUM THERETO IN THE DIRECTION OF SAID CHAMBER ONE END WALL, WHERE SAID MOTIVE FLUID PRESSURE, SAID PISTON MEMBER MASS, SAID PREDETERMINED DISTANCES, AND SAID PREDETERMINED TIME PERIOD ARE SUCH, RELATIVE TO ONE ANOTHER, THAT APPLICATION OF SAID MOTIVE FLUID TO SAID PISTON MEMBER WHEN AT SAID MAXIMUM DISTANCE FROM SAID CHAMBER ONE END WALL CAUSES SAID PISTON MEMBER TO HAVE MOMENTUM IN THE DIRECTION TOWARD SAID CHAMBER ONE END WALL SUFFICIENT TO CREATE A SECOND CHAMBER VOLUME VALUE LESS THAN SAID FIRST CHAMBER VOLUME VALUE. 